fix: automock getters and setters (#1903)

* fix: automock getters and setters

* refactor: do not mock getters/setters

Co-authored-by: Vladimir Sheremet <sleuths.slews0s@icloud.com>

examples/mocks/test/automocking.spec.ts

@@ -1,8 +1,10 @@
 import type * as exampleModule from '../src/example'
 import log from '../src/log'
+import { A } from '../src/moduleA'
 import { methodSymbol, moduleWithSymbol } from '../src/moduleWithSymbol'
 
 vi.mock('../src/log')
+vi.mock('../src/moduleA')
 vi.mock('../src/moduleWithSymbol')
 
 test('all mocked are valid', async () => {
@@ -55,3 +57,7 @@ test('automock properly restores mock', async () => {
   expect(moduleWithSymbol[methodSymbol]()).toBe('hello')
   expect(moduleWithSymbol.warn()).toBe('hello')
 })
+
+test('automock has a getter', () => {
+  expect(A).toBe('A')
+})

packages/vitest/src/runtime/mocker.ts

@@ -209,10 +209,14 @@ export class VitestMocker {
       const isModule = containerType === 'Module' || !!container.__esModule
       for (const { key: property, descriptor } of getAllMockableProperties(container)) {
         // Modules define their exports as getters. We want to process those.
-        if (!isModule) {
-          // TODO: Mock getters/setters somehow?
-          if (descriptor.get || descriptor.set)
-            continue
+        if (!isModule && descriptor.get) {
+          try {
+            Object.defineProperty(newContainer, property, descriptor)
+          }
+          catch (error) {
+            // Ignore errors, just move on to the next prop.
+          }
+          continue
         }
 
         // Skip special read-only props, we don't want to mess with those.

test/core/src/mockedC.ts

@@ -11,6 +11,10 @@ export class MockedC {
     return mockedA()
   }
 
+  get getOnlyProp(): number {
+    return 42
+  }
+
   get getSetProp(): number {
     return 123
   }

test/core/test/mocked.test.js

@@ -1,4 +1,4 @@
-// this file should not be converted to js
+// this file should not be converted to ts
 // so it won't be transformed by esbuild
 
 import { assert, test, vi } from 'vitest'

test/core/test/mocked.test.ts

@@ -13,6 +13,25 @@ vitest.mock('virtual-module', () => ({ value: 'mock' }))
 vitest.mock('../src/mockedC')
 vitest.mock('../src/mockedD')
 
+/**
+ * Get a property descriptor from an object.
+ *
+ * This is different from `Object.getOwnPropertyDescriptor` because it recurses
+ * into the prototype chain until it either finds a match or reaches the end.
+ *
+ * @param object The object that contains the property.
+ * @param property The property.
+ * @returns The property's descriptor, or undefined if no matching property was found.
+ */
+function getPropertyDescriptor(object: any, property: PropertyKey) {
+  for (let o = object; o; o = Object.getPrototypeOf(o)) {
+    const descriptor = Object.getOwnPropertyDescriptor(o, property)
+    if (descriptor)
+      return descriptor
+  }
+  return undefined
+}
+
 test('submodule is mocked to return "two" as 3', () => {
   assert.equal(3, two)
 })
@@ -58,6 +77,43 @@ describe('mocked classes', () => {
     expect(MockedC.prototype.doSomething).toHaveBeenCalledOnce()
     expect(MockedC.prototype.doSomething).not.toHaveReturnedWith('A')
   })
+
+  test('should mock getters', () => {
+    const instance = new MockedC()
+
+    expect(instance).toHaveProperty('getOnlyProp')
+    const descriptor = getPropertyDescriptor(instance, 'getOnlyProp')
+    expect(descriptor?.get).toBeDefined()
+    expect(descriptor?.set).not.toBeDefined()
+
+    expect(instance.getOnlyProp).toBe(42)
+    // @ts-expect-error Assign to the read-only prop to ensure it errors.
+    expect(() => instance.getOnlyProp = 4).toThrow()
+
+    const getterSpy = vi.spyOn(instance, 'getOnlyProp', 'get').mockReturnValue(456)
+    expect(instance.getOnlyProp).toEqual(456)
+    expect(getterSpy).toHaveBeenCalledOnce()
+  })
+
+  test('should mock getters and setters', () => {
+    const instance = new MockedC()
+
+    expect(instance).toHaveProperty('getSetProp')
+    const descriptor = getPropertyDescriptor(instance, 'getSetProp')
+    expect(descriptor?.get).toBeDefined()
+    expect(descriptor?.set).toBeDefined()
+
+    expect(instance.getSetProp).toBe(123)
+    expect(() => instance.getSetProp = 4).not.toThrow()
+
+    const getterSpy = vi.spyOn(instance, 'getSetProp', 'get').mockReturnValue(789)
+    expect(instance.getSetProp).toEqual(789)
+    expect(getterSpy).toHaveBeenCalledOnce()
+
+    const setterSpy = vi.spyOn(instance, 'getSetProp', 'set')
+    instance.getSetProp = 159
+    expect(setterSpy).toHaveBeenCalledWith(159)
+  })
 })
 
 describe('default exported classes', () => {